(1) Field of the Invention
The present invention relates to a liquid crystal display device, and in particular, to a semi-transmission type liquid crystal display device having a reflective display portion which also works as a transmissive display portion, as well as a manufacturing method for the same.
(2) Related Art Statement
Liquid crystal display devices have such advantages as to be thin and light, and consume little power in comparison with CRT's (cathode ray tubes), which are the mainstream for conventional display devices, and thus, have many applications as display devices, for various electronics. From among these, higher visibility has been required for display devices for portable information apparatuses in various environments, including dark places, such as indoors, places where there are no external light sources, and places with strong illumination, such as outdoors in fair weather, and thus, semi-transmission type liquid crystal display devices having a transmissive display portion and a reflective display portion within each pixel are widely used.
In semi-transmission type liquid crystal display devices, a backlight is used in transmissive display portions, so that the brightness is constant, irrespectively of the environment, and therefore, an appropriate display can be gained in relatively dark environments, such as indoors and in dark rooms. Meanwhile, reflective display portions provide a display through reflection of external light using a built-in reflective plate, and thus, the contrast is constant, irrespectively of the brightness outside, and therefore, an appropriate display can be gained in relatively bright environments, such as outdoors in fair weather, and indoors.
Meanwhile, IPS (in-plane switching) type liquid crystal display devices are conventional liquid crystal display devices, and known to have a wide view angle, and in the case where IPS types are applied to a semi-transmission type liquid crystal display devices, a problem arises, such that a dark display cannot be gained in reflective portions. In contrast, reflection type displays and transmission type displays are implemented when a polarizing layer is built in, as in the below described Patent Document 1.
In addition, the below described Patent Document 2 discloses a semi-transmission type liquid crystal display device of a twisted nematic (TN) type. In this semi-transmission type liquid crystal display device also, a polarizing layer is built-in, and thus, reflective display and transmission display are compatible.
In addition, the below described Patent Document 3 discloses transmission type and semi-transmission type liquid crystal display devices. These transmission type and semi-transmission type liquid crystal display devices have a built-in polarizer, and an interlayer insulating film is formed on top of the polarizing layer from a photosensitive resin, and thus, the image quality is better, the display device is compact, the yield in the manufacture is higher, the reliability high, and the process is simpler. Here, the built-in polarizing layers in the below described Patent Documents to 3 are formed by applying and curing an application liquid which includes the lyotropic liquid crystal described in the below Patent Document 4 as a polarizing material.    [Patent Document 1] Japanese Unexamined Patent Publication 2006-184325    [Patent Document 2] Japanese Unexamined Patent Publication 2006-171723    [Patent Document 3] Japanese Unexamined Patent Publication 2005-250430    [Patent Document 4] Japanese translation of International Unexamined Patent Publication H08 (1996)-511109